User`s guide

Chapter 3 3-11
Theory of Operation and Troubleshooting
Troubleshooting
The voltage on bias pins 1 and 2 should alternate between
+0.62 Vdc and +16.3 Vdc when the instrument is toggled from
REFL: FWD S11 (A/R) and REFL: REV S22 (B/R). If the bias voltage
changes state but there is still no RF at Port 2 in the forward state or
no RF at Port 3 in the reverse state, the transfer switch S1 may need
to be replaced.
Before replacing switch S1, check Port 2 and Port 3 in the receiver
section to make sure the test port couplers are functioning correctly.
If Port 2 and Port 3 are working correctly and the bias voltage
remains the same, check the LEDs to make sure the source test port
is being redirected. When the instrument is toggled from
REFL: FWD S11 (A/R) to REFL: REV S22 (B/R), the bright LED indicates
the incident port and the dim LED indicates the receiver port.
If the LEDs are working on Port 2 and Port 3 and the bias voltage is
still incorrect on switch S1, move the S0 bias connector from J3 to J6
(see Figure 3-17) on the test set interface board. Check the bias
voltage (+0.62 Vdc and + 16.3 Vdc) on S1 (see Figure 3-13). Toggle the
instrument between the REFL: FWD S11 (A/R) and REFL: REV S22 (B/R)
states. If the bias voltage does not change, replace the test set
interface board. If the bias voltage changes, replace S1.
Receiver Section Test
This section only covers the Option H39 area of the receiver. This is only
a function test to verify that an RF signal can be received by either the
A or B channel samplers. When making your measurements refer to
Figure 3-4, Figure 3-5, and Figure 3-6 as examples of an irregular or
degraded response.